Fast and furious: shorter handling times reveal a foraging advantage of the invasive Carcinus maenas over its native competitor Metacarcinus gracilis

Abstract

Invasive species have been shown to decrease the fitness of native species and reduce biodiversity. The European green crab (Carcinus maenas) is a prolific invasive crab species responsible for habitat degradation and biodiversity reduction across the globe, and has been present on Canada’s southwestern coast since the late 1990’s. Using feeding rates as a proxy for individual fitness, we examined how the rate of prey handling and consumption in C. maenas compares to that of the native graceful rock crab (Metacarcinus gracilis). The time required by C. maenas and M. gracilis to handle and consume a mussel (handling time) was compared at two flume velocities (10 and 19cm/s) to quantify feeding rates under differing flow conditions. These measurements have possible implications for how C. maenas populations may affect M. gracilis demography in coming years. At both flume speeds, C. maenas had a lower handling time than M. gracilis. At 10cm/s flow, C. maenas fed an average of 2 minutes faster than M. gracilis, whereas at 19cm/s they fed 5.2 minutes faster on average. These data suggest C. maenas is capable of more efficient foraging at a variety of current speeds. Handling time is widely recognized as an important influence on invasion success, and our findings thus suggest that C. maenas has a competitive advantage over M. gracilis across its native range. These results have implications for modeling the predicted spread of C. maenas along the coastal East Pacific.